Japanese Patent Laying-Open No. 2011-110065 (PTD 1) is a prior document disclosing how to assist high-accuracy magnetic-field adjustment for an MRI (Magnetic Resonance Imaging) apparatus.
According to the magnetic-field adjustment method disclosed in PTD 1, a magnetic field generating device has a region to which a target magnetic field distribution is set. An error magnetic field of the magnetic field distribution in this region is reduced to thereby make the magnetic field distribution close to the target magnetic field distribution. A current loop, a ferromagnetic material which is passively magnetized such as an iron piece, or a permanent magnet which does not depend on an external magnetic field is disposed to serve as adjusting means.
Specifically, the magnetic field is adjusted by taking a magnetic field measurement at a predetermined number of points, calculating an error magnetic field that is a difference from a target magnetic field, determining a current potential distribution in a region of a magnetic field adjustment mechanism that can approximately correct the error, converting the current potential distribution into magnetic moments, and arranging a loop current or a magnetic material piece that corresponds to the magnetic moments.